[PATCH 0/6] CPUoffline framework
amit.kucheria at linaro.org
Mon Aug 22 15:52:33 UTC 2011
On Mon, Aug 22, 2011 at 5:21 PM, Christian Robottom Reis
<kiko at linaro.org> wrote:
> On Mon, Aug 22, 2011 at 11:18:52AM -0300, Christian Robottom Reis wrote:
>> On Fri, Aug 19, 2011 at 12:38:13PM -0700, Mike Turquette wrote:
>> > This series is posted for posterity. It has been NAK'd by the community
>> > since CPU hotplug has been deemed an inappropriate mechanism for power
>> > capping.
>> I spoke with Amit about this last week. What's the plan going forward on
>> really saving power when a CPU isn't being used -- just ensuring the
>> lowest possible idle state is really off?
>> And are there situations where the hardware requires something like
>> hotplug to actually maximize savings?
> Oh, and finally, it seems that patches 1-3 might be useful, regardless
> of the NAKing of the actual patchset, right?
No, those were NACK'ed as well. The interface is not be 'enhanced' in
any way that might promote it's use for power savings.
Peter's actual message below:
"Nacked-by: Peter Zijlstra <a.p.zijlstra at chello.nl>
the kernel really shouldn't be using hotplug for this (nor should
userspace really). hot-unplugging random cpus wrecks things like
cpusets. Furthermore hotplug does way too much work to use as a simple
means to idle a cpu.
Even the availability of this mask is wrong, since that implies the
information is useful, which per the above it is not, the kernel
shouldn't care about this full-stop.
The only reason for the OS to unplug a CPU is imminent and unavoidable
hardware failure. Thermal capping is not that (and yes ACPI-4.0 is a
broken piece of shit)."
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